Vacuum device and method of manufacture



May 13, 1930;

H. C. RENTSCHLER VACUUI DEVICE "AND METHOD OF MANUFACTURE Filed Sept 27, 1924' M? H 4 r 2 Fee a w M m R w n/ R R m WW VY -T N m T I -A H such as molybdenum Patented May 13, 1930 UNITED STATES PATENT OFFICE HARVEY CLAYTON RENTSCHLER, OF EA WESTINGHOUSE LAMP, .COMPAN Y,

ST ORANGE, NEW JERSEY, ASSIGNOR TO A CORPORATION OF PENNSYLVANIA "VACUUM DEVICE AND METHOD OF MANUFACTURE Application filed September 27, 1924. Serial No. 740,409.

This application is a continuation-in-part of the copending application of Marden and Rentschler, Serial No. 67 9,489, filed December 8,1923, clean-up and activationby miseh metal and the rare earth metals, and assigned to the Westinghouse Lamp Company.

Thisinvention relates to vacuum devices and more particularly to those utilizing a metallic clean-up agent, such as misch metal or the like.

In electron devices of'the prior art, it has been common to employ a refractory metal as an electrode material. Such material has the disadvantage that it is expensive and rather diflicult to work.

To overcome these difficulties, nickel has been substituted for a more refractory electrode material. However, metallic clean-up agents, such as misch metal or the like, upon volatilization, attack the nickel when the latter is used as a carrier for agents of this I character.

I have discoveredthat nickel as electrode material may be replaced by iron, and that the latter is not deleteriously affected when the same functions as acarrier for a metallic clean-up agent upon volatilization thereof.

It is therefore an object of my invention to utilize iron as a carrier for a metallic clean: up agent embodied in evacuated electrical devices such as radio tubes, incandescent electric lamps and the like.

A more specific object of my invention is the use of iron as a plate material in radio tubes and the like, whereby certain metallic clean-up agents, suc has misch metal, may be secured thereto without the danger of causing injury or destruction thereto during the cleaning-up process, effected by heating or vol'atilization of the clean-up agent.

A further object of my invention is the manufacture of radio tubes with' plates, preferably constructed of relatively pure-iron, making use of misch metal as a clean-up material in the device, whereby the necessity for a C battery is dispensed with, as with such a 7 more strongly electropositive clean-up agents, such as magnesium. 2

\ Other objects and advantages of the invention will be apparent as the description proceeds.

In making an electron tube embodying my invention, no change is necessary in the man- 'ufacture thereof, other than substituting a plate of iron for one of nickel. It has been found that, contraryto what might be supno posed, no alloying results when the iron plate with misch metal or rare earth metal applied thereon in the usual manner, is heated to cause vaporization of the misch metal. I preferably use the best grade of Norway iron 5' to avoid introducing impurities into the bulb. In a number of tests, the heating was continued even after the misch metal was flashed sufficiently to clean-up the gases, in order to determine whether it was possible that such metal, at a still higher temperature, would attack the iron. In no case, however, did misch metal melt through the iron, as it did in similar instances with nickel. By the use of iron, I am enabled to make cheaper and yet better tubes. An advantage of misch metal, not secured by 'a usual material, such as magnesium, is that the grid current does not start in the tube until the potential of thegrid is positive, as so contradistinguished from the negative or zero potential at which the grid current starts when using magnesium or other more strongly electro-positive metal. 'As an illustration, ten tubes of the '20 1-A type with misch metal clean-up material had a value of the grid potential at which the grid current started, varying from .3 to 1.1 volts positive. The average was .62 volts positive. WVith a regular magnesium clean-up, the 9 grid potential varied from .4.- to +1 with an average of .1. It will be apparent, therefore, that in using misch metal according to my invention, a 0 battery becomes'unnecessary and one element in radio apparatus is.

therefore, dispensed with.

A possible explanation of the reason for this desirable etfectis that, if any misch metal is deposited on the grid during the activation thereof, it does not of itself, cause any grid operating characteristics, whereas,

current to start until the grid is made positive from an external source. In other words,

the de 'osition of misch metal, upon a grid forme of electronegative material such as molybdenum, does not appreciably afiieet its on the I contrary, if theclean-up agent is magnesium, calcium, sodium or some other more strongly electropositive metal, when the same becomes deposited on the grid, it so changes its operating characteristics that a grid current flows thereto because of its inherently positive surface, even though its potential from an outside source is zero or negative. Although this is advanced as a plausible explanation, I do not wish to be limited thereto, as the result stated is secured regardless of how it is effected;

In order that theinvention may be more fully understood reference may be had to the accompanying drawing in which the single figure discloses a three electrode electron discharge device embodying my invention.

In this view, envelope 1 containing a filamentary cathode 2, grid or control electrode 3 and anode 4 is shown. A quantity 5 of misch metal or other'metal of the cerium group of rare earth metals is secured to the anode 4 in any convenient manner. The anode is formed of iron which is stable with respect to the getter 5 and which permitsthe getter to be vaporized therefrom without causing injury or destruction thereto. Upon vaporization, a portion of the misch metal is vaporized onto the grid and gives a negative bias so that the grid current does not start until the grid is made positive from an external source.

Although I have described my invention particularly with reference to radio tubes and I other electron devices, it is to be understood that I contemplate using misch metal and the like for cleaning up residual gases in other evacuated devices, for example, incandescent electric lamps, by applying the same to a carrier formed of iron and heating said carrier in the evacuated device to vaporize or sufficiently heat the same to-effect the desired clean-up action.

The expression .rare earth metal of the cerium group is used herein to designate in accordance with accepted classification, cerium, lanthanum, praseodymium, neodymium and Samarium.

Although I have described what is now considered a preferredembodiment of my invention, it is to be understood that the same is merely illustrative and that other modifications may occur to those skilled in the art within the spirit and scope of theappended claims.

What is claimed is:

1. An evacuated container having therein a rare earth metal of the cerium group and a metallic member to which said rare earth metal is attached, said metallic member being adapted to be heated, to a sufiiciently high temperature to vaporize said rare earth metal and being composed of iron with WhlCh said rare earth metal does not deleteriously react durin such vaporization.

2. in evacuated containerhaving therein a quantity of misch metal and a metallic member to which said -misch metal is attached, said --metallic member being adapted to be heated to a sufficiently high temperature to vaporize said misch metal and being composed of iron with which said misch metal does not deleteriously react during such vaporization.

3. Anelectrode for a vacuum device having a quantity of misch metal attached thereto, said electrode being composed of iron.

In testimony whereof, I have hereunto subscribed my name this 25th day of September,

1924a HARVEY CLAYTON RENTSGHLER. 

